Cochlear implants provide auditory stimulation for deaf individuals through direct electrical stimulation of the auditory nerve. Electrical stimulation of the auditory nerve results in highly synchronized neural responses. One consequence of high neural synchrony may be a narrow dynamic range of hearing. The long-term objective of this project is to examine the potential benefits of high-rate pulse trains for cochlear implant users, particularly regarding percepts related to stimulus level and dynamic range of hearing. In the future this information may help improve the quality of hearing and quality of life for deaf individuals with cochlear implants. The specific aims of this study are: 1) to examine the effects of high-rate pulse trains on intensity discrimination of sinusoidal stimuli; 2) to investigate the effects of high-rate pulse trains on electrode discrimination of sinusoidal stimuli; and 3) to examine the effects of high-rate pulse trains on intensity discrimination of low-rate pulse stimuli. The hypotheses of the Specific Aims are that high-rate pulse trains will improve intensity discrimination for sinusoids and pulses, and will improve electrode discrimination. The research design and methods for this study include cochlear implant subjects with the Clarion Cll device, using the Advanced Bionics Bionic Ear Data Collection System (BEDCS). Specific Aims 1 and 3 will be investigated by measuring sensitivity to intensity changes from a single electrode, and Specific Aim 2 will be examined by measuring the ability of cochlear implant users to discriminate between stimuli presented to two different electrodes. Both discrimination tasks will be measured at several stimulation levels, with and without high-rate pulse trains. The data analyses will focus on comparisons between discrimination ability, with and without high-rate pulse trains.